Watercraft with improved characteristics for travel in ice

ABSTRACT

The invention relates to a watercraft having improved characteristics for travel in ice, particularly an icebreaker, supply vessel, cargo vessel or corresponding, which watercraft has a hull, which has at the stem portion a propulsion and steering arrangement, which is mainly responsible for movement and steering of the watercraft and which includes at least one skeg-like projection, in which is located at least one propeller device. In accordance with the invention, said skeg-like projections comprise two units located on different sides of the centre line of the hull. Said propeller device is located at the stem end of the skeg-like projection. In addition, the skeg-like projection has between the propeller device and the hull of the watercraft, in the longitudinal direction on the skeg-like projection, one or more thruster devices to provide a water flow mainly transverse in relation to the hull.

The invention relates to a watercraft according to the preamble of claim 1 with improved characteristics for travel in ice, particularly an icebreaker, supply vessel, cargo vessel or corresponding, which watercraft has a hull, which has at the stern portion a propulsion and steering arrangement, which is mainly responsible for the movement and steering of the vessel and which includes at least one skeg-like projection, in which is located at least one propeller device.

The steerability of an icebreaker or a supply ship or corresponding working in ice-covered water is an extremely important characteristic. Traditionally, the vessel is equipped with one or more propellers and a rudder located behind it. An extremely efficient alternative propulsion and steering arrangement is a turnable steering thruster device. The patent Fl 94508 presents one solution, in which the vessel moves under difficult ice conditions stern forward utilizing steering thrusters.

As the main propellers of a ship can be used traditional propeller shaft solutions, in which the driving mechanism inside the hull of the vessel rotates the propeller via a propeller shaft that is led through the hull and is often quite long. To increase the efficiency of steering, under these circumstances, it is common to equip the vessel with a thruster installed in a transverse tunnel, by which is provided a transverse water flow and steering reaction force. These kinds of propellers are generally installed in the bow of a vessel, but also in the area of the stern, in a middle skeg or side skegs independent of the ordinary propeller shaft lines.

In steering thruster solutions, neither tunnel thrusters nor rudders are usually needed. The propeller drives are arranged either inside a turnable pod, or the operation is arranged via shafts and angle gears by a motor located in the hull of the ship.

It is obvious that the dimensions and structure of the components, which will be in contact with ice, must be selected taking into consideration the stress created by the ice.

Although a steering thruster device is quite efficient solution for propulsion device and for steering of a ship, cases do occur, in which significant problems are related to its use. Such cases are the loads created by particularly thick and/or multi-year ice. In these cases, an arrangement is often selected, which has one or more traditional propellers and propeller shafts. To assure steerability, also at a slow travelling speed and when the ship is stationary, it is, in this case, necessary to use transversely installed tunnel thrusters.

FIGS. 1 a, 1 b and 1 c show an arrangement, which has two shaft lines 2 and 3 and one middle skeg 6, in which is located two tunnel thrusters 7 a and 7 b. In this arrangement, the operating ability of the vessel in ice is weakened due to the fact that the middle skeg hinders the free movement of broken ice chunks. Support from below for the rudder and a possible propeller nozzle is also difficult to implement, which is likely to weaken the ability of the structure to withstand ice chucks when travelling in icy waters.

An object of the invention is to provide a watercraft having improved characteristics for travel in ice and which minimizes the problems of known art described above. In particular, an object is to attempt to secure the steerability of the watercraft under ice conditions as well as to improve its ability to withstand the stress inflicted on the structures of the watercraft by ice and ice chunks.

The objects of the invention are mainly achieved in the manner presented in claim 1 and more in detail in the other claims. In accordance with the invention, a watercraft is equipped with two skeg-like projections, which are located on different sides of the centre line of the vessel at a distance from each other. The propeller device is attached to the stern end of the skeg-like projection or to the hull of the vessel onto the stern side of the skeg-like projection and, additionally, the skeg-like projection has between the propeller device and the hull of the watercraft, in the longitudinal direction on the skeg-like projection, one or more thruster devices to provide a water flow mainly transverse in relation to the hull.

The arrangement according to the invention is based on the fact that a propeller device located in or in connection with a skeg-like projection is selected such that the space required by its propeller shaft, in the longitudinal direction of the skeg-like projection, is so short that between the propeller device and the hull of the watercraft can be located one or more thruster devices to assure the steerability of the watercraft. The solution also enables as free as possible movement of broken ice chunks under the watercraft between the skeg-like projections, because, due to the solution according to the invention, there is enough space under the hull so that they can be located adequately far from each other. In addition, by using the thruster devices of different skeg-like projections in opposite directions outward from the hull, there can be provided a water flow substantially transverse in relation to the hull, by which the board of the watercraft can be flushed to reduce the friction between the hull and the ice and ice chunks, and, secondly, to clear the ice chunks from the channel broken in the ice field.

The propeller device can be implemented in various ways. For this purpose can be used a steering thruster device or corresponding, the turning of which in relation to the skeg-like projection is prevented. In this case, the propeller device receives its immediate operating power from an electric motor, which can be located in the skeg-like projection, for example, at the stern side of said one or more thruster devices. The electric motor can be in the immediate vicinity of the propeller or so short a propeller shaft is used for the purpose that the solution according to the invention can be implemented. Naturally, the electric motor can also be located, conventionally, on the deck above the propeller device or in a space specifically reserved for it, from which power is transferred in a manner known per se by using a vertical shaft and an angle gear mechanism.

Said thruster device can also be implemented in various ways. The thruster device can preferably be a tunnel thruster, which is most preferably arranged such that the water flow it provides is directed diagonally upwards. This is likely to increase the efficiency of the flushing effect it provides.

Preferably, the thruster device can also be movable from the first position, in which it is, at least mainly, inside the skeg-like projection, into the second position, in which it is, at least mainly, pushed out from the skeg-like projection. In addition, the thruster device can be arranged to be rotated in relation to the mainly vertical shaft thereof extending in the direction of movement. Thus, the thruster device can function in the manner of a tunnel thruster, when being in the retracted position, and when in the lowered-down position, it can respectively function as a steering and propulsion device. Also in this case it is preferred that the water flow provided by the thruster device is directed diagonally upward.

Attached to the hull, there can also be a rudder device on the stern side of said propeller device. The propeller device, in turn, can be equipped with a nozzle surrounding the propeller, as needed. In this case, said nozzle and most preferably also said rudder device can preferably be supported to said skeg-like projection from below. This is prone to strengthen the ability of the structures to withstand the stress applied thereto by the ice chunks.

In the following, the invention is described by way of example with reference to the accompanying schematical drawings, in which

FIGS. 1 a, 1 b and 1 c show a known propulsion and steering arrangement of the stern portion of a known watercraft, as viewed obliquely from below, from the side and from below and partially in cross-section,

FIGS. 2 a, 2 b and 2 c show a first embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and from below and partially in cross-section,

FIGS. 3 a, 3 b and 3 c show a second embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and from below and partially in cross-section,

FIGS. 4 a, 4 b and 4 c show a third embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and from below and partially in cross-section,

FIGS. 5 a, 5 b and 5 c show a fourth embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and from below and partially in cross-section,

FIGS. 6 a, 6 b and 6 c show a fifth embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and from below and partially in cross-section, and

FIGS. 7 a, 7 b and 7 c show a sixth embodiment of the invention, in which the propulsion and steering arrangement of the stern portion of the watercraft is shown obliquely from below, from the side and frombelow and partially in cross-section.

FIGS. 1 a, 1 b and 1 c show an arrangement, in which the stern portion of the hull 1 of the watercraft has two shaft lines 2 and 3 and one middle skeg 6. The shaft lines 2 and 3 include propellers 2 a and 3 a and nozzles 2 b and 3 b surrounding them, as well as propeller shafts 2 c and 3 c, which connect the propellers to motors 2 d and 3 d. The middle skeg 6 has tunnel openings 6 a and 6 b for tunnel thrusters 7 a and 7 b. Associated with the shaft lines are additionally rudders 4 and 5. Disadvantages of the solution are described above in the section relating to prior art.

FIGS. 2-7 show various alternative solutions for the invention. These have in common that the stern portion of the hull 1 of the watercraft has two skeg-like projections 8 and 9, which are equipped with propeller devices 10 and 11, which are attached to the skeg-like projections 8 and 9 such that the propellers 10 a and 11 a they include cannot be turned in relation to the skeg-like projections in question. In addition, on the stern side of the skeg-like projections, there are rudder devices 4 and 5. Alternatively, the propeller devices can be located in connection with the skeg-like projections, on the stern side of them and can be turned to a limited extent in relation to the skeg-like projections in question.

The propeller devices 10 and 11 are selected and their power transmission is arranged such that there is no need for a long power transmission shaft extending along the skeg-like projection. In practise, power is obtained via electric motors in a manner known per se, so it is not further described here. Thus, in front of the propulsion units of the skeg-like projections 8 and 9 in relation to the hull of the watercraft, there are, additionally, situated different types of thruster devices 12, 12′ or 12″, which provide water flows transverse in relation to the skeg-like projections 8 and 9. By utilizing these, it is possible to improve the steerability of the watercraft as well as its properties for travel in ice depending on the direction, in which the water flows are directed. Accordingly, for example, the board of the watercraft can be flushed to reduce the friction between the hull and ice and ice chunks by guiding the water flow upward from the hull, or the ice chunks can be cleaned from the channel broken in the ice field.

In the embodiment of FIGS. 2 a, 2 b and 2 c, as the thruster devices are used tunnel thrusters 12 and 13, which are located in transverse tunnel openings 8 a and 9 a of the skeg-like projections. As needed, there can also be several tunnel thrusters in each of the skeg-like projections.

The embodiment of FIGS. 3 a, 3 b and 3 c differs from the previous embodiment in that, around the propellers, there are nozzles 10 b and 11 b, which direct the water flow provided by the propellers and, at the same time, protect the propellers. In addition, the rudder devices 4 and 5 as well as the nozzles 10 b and 11 b are supported from below by support elements 8 c and 9 c, which are attached to the lower part of the skeg-like projections 8 and 9. Support of this type is prone to substantially strengthen the structure against the stress created by ice chunks. If desired, the support can also extend only to the nozzles.

In the embodiment of FIGS. 4 a, 4 b and 4 c propeller units 12′a and 13′a serve as thruster devices 12′ and 13′ and they are driven by motors 12′b and 13′b and can be lowered from inside to down below skeg-like projections 8 and 9. In their retracted position, these devices are located in vertical tunnel openings 8 b and 9 b in the skeg-like projections 8 and 9. In their protruding position, these propeller units can be rotated around their shaft, wherein water flows can, as needed, respectively be directed in different directions.

The embodiment of FIGS. 5 a, 5 b and 5 c differs from the embodiment of FIGS. 4 just as the embodiment of FIGS. 3 differs from the embodiment of FIGS. 2, i.e. here as well, the propellers 10 a and 11 a are equipped with nozzles 10 b and 11 b and, additionally, the solution is equipped with support elements 8 c and 9 c.

In the embodiment of FIGS. 6 a, 6 b and 6 c, the thruster devices 12″ and 13″ are likewise ones that can be lowered down. In this case they have, however, two operating positions; when lowered down from the tunnel openings 8 b and 9 b, the propeller units 12″a and 13″a function as in the embodiment of FIG. 5, but in their retracted position, they affect via the transverse tunnel openings 8 a and 9 a like conventional tunnel thrusters. Both operating positions are shown on top of each other in FIG. 6 b.

Once again, in the embodiment of FIGS. 7 a, 7 b and 7 c, the propellers 10 a and 11 a are equipped with nozzles 10 b and 11 b and, additionally, the solution is equipped with support elements 8 c and 9 c.

Depending on need and use of space, in all embodiments, it can be used one or more of the above-described thruster device versions 12, 12′ and 12″ in each of the skeg-like projections 8 and 9.

The invention is not limited to the embodiments presented but many variations are conceivable within the scope of the appended claims. 

1. A watercraft having improved characteristics for travel in ice, in particular an icebreaker, supply vessel, cargo vessel or corresponding, which watercraft has a hull, which has at the stern portion a propulsion and steering arrangement, which is mainly responsible for movement and steering of the watercraft and which includes at least one skeg-like projection, in which is located at least one propeller device, said skeg-like projections comprise two units situated on different sides of the centre line of the hull, said propeller device is located at the stern end or on the stern side of the skeg-like projection and the skeg-like projection has between the propeller device and the hull of the watercraft, in the longitudinal direction of the skeg-like projection, one or more thruster devices to provide a water flow mainly transverse in relation to the hull.
 2. A watercraft according to claim 1, wherein said propeller device is a steering thruster device or corresponding, the turning of which in relation to the skeg-like projection is prevented.
 3. A watercraft according to claim 1, wherein said propeller device receives its immediate operating power from a motor, which is located in the skeg-like projection on the stern side of said one or more thruster devices.
 4. A watercraft according to claim 1, wherein said propeller device receives its immediate operating power in a manner known per se by using a vertical shaft and an angle gear mechanism from a motor, which is located on the stern side of one or more thruster devices located in the skeg-like projection.
 5. A watercraft according to claim 1, wherein said thruster device is a tunnel thruster, which is most preferably arranged such that the water flow it provides is directed diagonally upward.
 6. A watercraft according to claim 1, wherein said thruster device is movable from the first position, in which it is, at least mainly, inside the skeg-like projection, into the second position, in which it is, at least mainly, pushed out from the skeg-like projection.
 7. A watercraft according to claim 6, wherein said thruster device can be rotated in relation to the mainly vertical shaft thereof extending in the direction of movement.
 8. A watercraft according to claim 6, wherein said thruster device is arranged to function in the manner of a tunnel thruster, when being in the retracted position, wherein it is most preferably arranged such that the water flow it provides is directed diagonally upward.
 9. A watercraft according to claim 1, wherein the hull has a rudder device on the stern side of said propeller device.
 10. A watercraft according to claim 1, wherein said propeller device is equipped with a nozzle surrounding the propeller.
 11. A watercraft according to claim 9, wherein said nozzle and most preferably also said rudder device are supported from underneath thereof to said skeg-like projection. 